Paul Berry
c800a1cc29
Previously, the front end recovered from an invalid assignment by
producing an "as" expression, e.g.:
int x;
String y;
x = y;
Would produce an "invalid assignment" error, as well as this kernel
code:
int x;
String y;
x = y as{TypeError} int;
The rationale was that the "as" check was guaranteed to fail, so this
code would produce a runtime error at the correct location. However,
there were two problems:
1. (Minor problem) the "as" doesn't actually fail if the RHS is null.
2. (Major problem) for type inference, the type of an assignment
expression is defined to be the type of the RHS. This means that if
the invalid assignment gets used for type inference, we generate
mal-typed kernel code, e.g.:
int x;
String y;
var z = (x = y);
Gets compiled to:
int x;
String y;
String z = (x = y as{TypeError} int);
This CL addresses both problems by changing the kernel representation
so that it evaluates the RHS and then throws an exception. Since a
"throw" expression has type Bottom, the kernel representation is
guaranteed to be properly typed. This also ensures that an exception
gets thrown if the RHS is null. Finally, as a side bonus, it makes
the error-recovered kernel code more similar to the kernel code we
generate in other error recovery scenarios.
Change-Id: Iac74e0c726ce029ac0560d271413e85c15bfec5c
Reviewed-on: https://dart-review.googlesource.com/24140
Reviewed-by: Kevin Millikin <kmillikin@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
Dart Kernel
Dart Kernel is a small high-level language derived from Dart. It is designed for use as an intermediate format for whole-program analysis and transformations, and as a frontend for codegen and execution backends.
The kernel language has in-memory representations in Dart and C++, and can be serialized as binary or text.
Both the kernel language and its implementations are unstable and are under development.
This package contains the Dart part of the implementation and contains:
- A transformable IR for the kernel language
- A frontend based on the analyzer
- Serialization of kernel code
Note: The APIs in this package are in an early state; developers should be careful about depending on this package.
Getting Kernel
Checkout the repository and run pub get:
git clone https://github.com/dart-lang/kernel
cd kernel
pub get
Command-Line Tool
Run tool/dartk.dart from the command-line to convert between .dart files
and the serialized binary and textual formats.
dartk expects the .dill extension for files in the binary format.
The textual format has no preferred extension right now.
Example commands:
dartk foo.dart # print text IR for foo.dart
dartk foo.dart -ofoo.dill # write binary IR for foo.dart to foo.dill
dartk foo.dill # print text IR for binary file foo.dill
Pass the --link or -l flag to link all transitive dependencies into one file:
dartk myapp.dart -ppackages -l -omyapp.dill # Bundle everything.
dartk myapp.dill # Print it back out in a (very, very long) textual format.
See ast.dart for the in-memory IR, or binary.md for a description of the binary format. For now, the textual format is very ad-hoc and cannot be parsed back in.
Testing
If you plan to make changes to kernel, get a checkout of the Dartk SDK and run:
tool/regenerate_dill_files.dart --sdk <path to SDK checkout>
pub run test
Linking
Linking from binary files is not yet implemented. In order to compile a whole program, currently everything must be compiled from source at once.